In a typical wireless communication system, wireless terminal equipment (TE) devices access a host computer through various access point (AP) devices. The AP devices communicate with the TE devices using a wireless communication protocol, and communicate with the host computer using some other protocol, such as a local area network (LAN) protocol. Each communication protocol is typically composed of various protocol layers in what is often referred to as a protocol stack. The protocol layers are typically implemented in software, and require certain processing resources as well as certain memory resources (e.g., for the storage of state information and data). The AP devices typically support and implement the full wireless communication protocol stack, and therefore the AP devices are typically complex devices that require substantial processing and memory resources.
One wireless communication protocol is commonly known as Bluetooth. Bluetooth defines a wireless (RF) protocol layer as well as various combinations of higher protocol layers (referred to in Bluetooth as profiles) for using Bluetooth in various applications. Bluetooth is described in a Bluetooth core specification entitled Specification of the Bluetooth System Core, Volume 1.0 B, dated Dec. 1, 1999, which is hereby incorporated herein by reference in its entirety. Bluetooth profiles are described in a Bluetooth profiles specification entitled Specification of the Bluetooth System Profiles, Volume 1.0 B, dated Dec. 1, 1999, which is hereby incorporated herein by reference in its entirety. For convenience, the Bluetooth core specification and the Bluetooth profiles specification are referred to hereinafter collectively as the Bluetooth specification.
FIG. 1 shows a representation of a conventional wireless communication system 100 in accordance with an implementation of Bluetooth. The TE device 102 accesses the host computer 108 via the AP device 106, using a wireless communication protocol to communicate with the AP device 106 over a wireless medium 104 (e.g., RF through air, infrared through air).
The AP device 106 typically implements the full wireless communication protocol stack. Therefore, the AP device 106 is typically a complex device having substantial processing and memory resources.
FIG. 2 illustrates the various protocol stacks that are supported and implemented by the TE device 102, the AP device 106, and the host computer 108 within the conventional wireless communication system 100 in accordance with a LAN Access Profile of the Bluetooth specification.
The TE device 102 includes, among other things, baseband transceiver logic 202 with associated host controller interface (HCI) firmware 204 for sending and receiving protocol messages over the wireless medium 104, HCI driver logic 206, logical link control and adaptation protocol (L2CAP) logic 208 for providing connection-oriented or connectionless layer 2 services, link manager protocol (LMP) logic 210, service discovery protocol (SDP) logic 212, RF communication logic 214 for emulating multiple RS-232 connections over L2CAP, Point-to-Point Protocol (PPP) logic 216, Internet Protocol (IP) logic 218, TCP/UDP logic 220, and a number of applications 222.
The AP device 106 includes, among other things, a first protocol stack for communicating with the TE device 102 and a second protocol stack for communicating with the host computer 108. The first protocol stack includes, among other things, baseband transceiver logic 224 with associated HCI firmware 226 for sending and receiving protocol messages over the wireless medium 104, HCI driver logic 228, L2CAP logic 230, LMP logic 232, SDP logic 234, RF logic 236, PPP logic 238, IP logic 240, and Dynamic Host Configuration Protocol (DHCP) logic 242. The second protocol stack includes, among other things, LAN logic 244, IP logic 240, Proxy ARP (Address Resolution Protocol) logic 246 for resolving addresses, and AAA (authentication, authorization, and accounting) logic 248.
The host computer 108 includes, among other things, LAN logic 250, IP logic 252, TCP/UDP logic 254, and a number of applications 256.
The wireless communication system typically includes mechanisms by which the AP devices decide which AP device is to handle communications for the TE device. For example, the TE device may be given access to the host computer through the closest AP device based upon some predetermined criteria (e.g., receive signal strength).
During operation of the wireless communication system, it may become necessary or desirable for the TE device to access the host computer through different AP devices at different times. For example, as the TE device moves about within the wireless communication system, the proximity of the TE device to various AP devices changes, making it necessary or desirable to move communications from an old AP device to a new AP device. Similarly, certain network events may disrupt communications between the TE device and the host computer (e.g., a communication failure between the TE device and the AP device, a failure or inactivation of the AP device, or a communication failure between the AP device and the host computer), making it necessary or desirable to move communications from the old AP device to the new AP device.
The wireless communication protocol typically includes mechanisms for moving communications from an old AP device to a new AP device. For convenience, this movement of communications from the old AP device to the new AP device is referred to herein as a “hand-off” from the old AP device to the new AP device. A “hand-off” from the old AP device to the new AP device may involve such things as determining the new AP device for the TE device (e.g., determining the next-closest AP device to the TE device) and moving communications from the old AP device to the new AP device.
Because the AP devices typically implement the full wireless communication protocol, the AP device through which the TE device accesses the host computer typically maintains substantial state information relating to the TE device. When there is a “hand-off” from the old AP device to the new AP device, state information maintained by the old AP device is lost, and the new AP device must re-establish communications for the TE device anew. Thus, the “hand-off” from the old AP device too the new AP device may substantially disrupt communications between the TE device and the host computer. In a Bluetooth wireless communication system implemented according to current specifications, it would not be uncommon for this disruption to last an unacceptably long 5-10 seconds.